Novel caged dopamine compounds. The abnormal regulation of dopamine receptors has been postulated as a prominent pathophysiology of several mental disorders, such as schizophrenia, bipolar disorder and depression. However, how dopamine receptors modulate information flow in individual neurons and neuronal circuits in prefrontal cortex is still poorly understood. Local activation of receptors in living neurons cn be achieved by two-photon photorelease of caged compounds. Indeed, two-photon uncaging of glutamate has revolutionized current understanding of excitatory transmission and integration in mammalian neurons. Unfortunately, opto-chemical tools to photorelease dopamine are scant, even though they would be extremely useful to study the function of dopaminergic modulation. We propose to use a newly synthesized caged compound, RuBi-Dopa, which can be photoreleased with two-photon lasers, to optically activate dopamine receptors with high precision and map the distribution of functional dopamine responses in spines from prefrontal pyramidal neurons, studying how their activation alters glutamatergic transmission. Finally, we will test how dopamine affects the temporal patterns of multi-neuronal firing in prefrontal cortex, by uncaging RuBi-Dopa while performing two-photon calcium imaging in vivo in awake preparations. The proposed work will expand the chemical toolbox of biological uncaging to include novel high-quality caged dopamine compounds that can be photo- released with two-photon lasers. These new compounds will enable the detailed investigation of the functional effects of dopaminergic transmission on selective subcellular compartments, something likely to have a major impact on our understanding of how dopamine alters normal and diseased brain function. It is possible that some of these compounds could be used to develop optical therapies for mental disease. Finally, our data will reveal, for the first time, the functional efect of dopaminergic inputs onto dendritic spines. Since spines mediate most excitatory connections, these results could also alter our understanding of how excitatory inputs are integrated.